Field of the Invention
The present invention relates to a system and method of charging a vehicle and a system and method of managing power consumption in a vehicle, and more particularly, a system and method of charging a vehicle using a dynamic power grid and a system and method of managing power consumption in a vehicle which optimizes a plurality of parameters based on a plurality of power source signatures for a plurality of power sources.
Description of the Related Art
Charging a Vehicle
Charging an electric vehicle on a power grid conventionally requires a tradeoff between the power delivery capacity of the grid and the desired charging times of all vehicles charging on the grid.
Batteries in battery electric vehicles (BEVs) must be periodically recharged. Most commonly, these vehicles charge from the power grid (at home or using a street or shop charging station), which is in turn generated from a variety of domestic resources such as coal, hydroelectricity, nuclear and others. Home power such as roof top photovoltaic solar cell panels, microhydro or wind may also be used and are promoted because of concerns regarding global warming.
Charging time is limited primarily by the capacity of the grid connection. A normal household outlet may range from 1.5 kW (in the US, Canada, Japan, and other countries with 110 volt supply) to 3 kW (in countries with 220/240V supply). The main connection to a house might be able to sustain 10 kW, and special wiring can be installed to use this. At this higher power level charging, even a small, 7 kW·h (22-45 km) pack, would generally requires a one hour charge.
In 1995, some charging stations charged BEVs in one hour. In November 1997, a fast-charge system charged lead-acid batteries in between six and fifteen minutes. In February 1998, one system could recharge NiMH batteries in about ten minutes, providing a range of 60 miles to 100 miles (100 km to 160 km). In 2005, mobile device battery designs by one manufacturer were claimed to be able to accept an 80% charge in as little as 60 seconds.
Scaling this specific power characteristic up to the same 7 kW·h EV pack would result in the need for a peak of 340 kW from some source for those 60 seconds. It is not clear that such batteries will work directly in BEVs as heat build-up may make them unsafe.
Today, a conventional battery can be recharged in several minutes, versus hours required for other rechargeable batteries. In particular, a cell in this conventional battery can be charged to around 95% charge capacity in approximately 10 minutes.
The charging power can be connected to the car in two ways using an (electric coupling). The first approach is a direct electrical connection known as conductive coupling. This might be as simple as a mains lead into a weatherproof socket through special high capacity cables with connectors to protect the user from the high voltage. Several standards, such as SAE J1772 and IEC 62196, cohabit.
The second approach is known as inductive charging. A special paddle is inserted into a slot on the car. The paddle is one winding of a transformer, while the other is built into the car. When the paddle is inserted, it completes an electromagnetic circuit which provides power to the battery pack. In one inductive charging system, one winding is attached to the underside of the car, and the other stays on the floor of the garage.
The major advantage of the inductive approach is that there is no possibility of electric shock as there are no exposed conductors, although interlocks, special connectors and RCDs (ground fault detectors) can make conductive coupling nearly as safe. An inductive charging proponent from one manufacturer contended in 1998 that overall cost differences were minimal, while a conductive charging proponent from Ford contended that conductive charging was more cost efficient.
Power Consumption in the Vehicle
A vehicle such as a plug-in hybrid electric vehicle (PHEV) may derive power from two or more on-board power storage systems. The first is a rechargeable battery that can be charged by: 1) the internal-combustion engine, 2) regenerative braking, as in a traditional hybrid vehicle, or 3) connecting a plug to an external electric power grid, a feature unique to PHEV. The second storage system is a traditional fuel tank for the storage of liquid hydrocarbon fuels used to power the internal-combustion engine. Because of the PHEV's capacity to store power from both liquid fuels and the electric power grid, the range of actual energy sources for powering the vehicle is virtually limitless. These sources include, but are not limited to gasoline, ethanol, coal, nuclear, solar, hydro-electric, and wind.
Thus, the electricity used to recharge the battery can come from many sources, depending on the time of day or location of the vehicle. For example, in one region of the country, hydroelectric power may be prevalent. This is a form of “clean” energy. However, in another region of the country, coal may be used. Thus, the recharging of an electric vehicle may be considered relatively “green” (e.g. low carbon creation) or “not green” (e.g. high carbon creation). This means that the same vehicle might be considered to have low environmental impact or high environmental impact.
The impact of each of these power sources on the environment is different, especially with regard to a measure that has grown in importance due to models which predict a human-origin for global warming in the coming decades: the amount of fossil carbon emitted. Thus, PHEV impact varies according to numerous “external” sources
Further, the blend of power consumed by a PHEV from either the on-board battery or liquid fuel tank is typically managed by selection of one of several Operating Modes which may include, for example, a charge-depleting mode, a blended mode, a charge-sustaining mode and a mixed mode.
The charge-depleting mode allows a fully charged PHEV to operate exclusively (or depending on the vehicle, almost exclusively, except during hard acceleration) on electric power until its battery state of charge is depleted to a predetermined level, at which time the vehicle's internal combustion engine or fuel cell will be engaged. This period is the vehicle's all-electric range. This is the only mode that a battery electric vehicle can operate in, hence their limited range.
The blended mode is a kind of charge-depleting mode. It is normally employed by vehicles which do not have enough electric power to sustain high speeds without the help of the internal combustion portion of the powertrain. A blended control strategy typically increases the distance from stored grid electricity vis-a-vis the charge-depleting strategy.
The charge-sustaining mode is used by production hybrid vehicles (HEVs) today, and combines the operation of the vehicle's two power sources in such a manner that the vehicle is operating as efficiently as possible without allowing the battery state of charge to move outside a predetermined narrow band. Over the course of a trip in a HEV the state of charge may fluctuate but will have no net change.
The mixed mode describes a trip in which a combination of the above modes are utilized. For example, a PHEV conversion may begin a trip with 5 miles (8 km) of low speed charge-depleting, then get onto a freeway and operate in blended mode for 20 miles (32 km), using 10 miles (16 km) worth of all-electric range at twice the fuel economy. Finally, the driver might exit the freeway and drive for another 5 miles (8 km) without the internal combustion engine until the full 20 miles (32 km) of all-electric range are exhausted. At this point the vehicle can revert back to a charge sustaining mode for another 10 miles (16 km) until the final destination is reached. Such a trip would be considered a mixed mode, as multiple modes are employed in one trip. This contrasts with a charge-depleting trip which would be driven within the limits of a PHEV's all-electric range. Conversely, the portion of a trip which extends beyond the all-electric range of a PHEV would be driven primarily in charge-sustaining mode, as used by a conventional hybrid.
Thus, considering the power sources for charging electric vehicles, some have asked whether electric vehicles really are a better environmental choice. In a recently published article, the author noted that driving 60 miles in a day and charging an electric car in Albany, N.Y. where electric energy is relatively clean, would only result in about 18 lb of carbon dioxide being emitted over the course of the day, whereas a gas powered car that gets 30 miles to the gallon would result in 47 lb over the same 60 miles. However, charging an electric car in Denver, Colo. which is powered by higher levels of coal, would actually emit the same levels of carbon dioxide as the comparable gas powered car.